The present invention relates in general to a field-emission display, and more particularly, to compensation of luminescent brightness of sub-pixels of a field-emission display.
The field-emission display (FED) is a very newly developed technology. Being self-illuminant, such type of display does not require a back light source like the liquid crystal display (LCD). In addition to the better brightness, the viewable angle is broader, power consumption is lower, responding speed is faster (no residual image), and the operation temperature range is larger than currently available flat displays. The image quality of the field-emission display is similar to that of the conventional cathode ray tube (CRT) display, while the dimension of the field-emission display is much thinner and lighter than the cathode ray tube display. Therefore, it is foreseeable that the field-emission display will replace the liquid crystal display and plasma display panel in the future. Further, the fast growing nanotechnology enables nano-material to be applied in the field-emission display, such that the technology of field-emission display will be commercially available in the near future.
FIG. 1 shows a cross sectional view of a basic tri-electrode based field-emission display essentially consisting of an anode plate 10, a cathode plate 20 and a gate layer 25. The anode plate 10 and the cathode plate 20 are supported by a spacer 14. The anode plate 10 includes an anode substrate 11, an anode conductive layer 12 and a phosphor layer 13. The cathode plate 20 includes a cathode substrate 21, a cathode conductive layer 22, an electron-emission source layer 23 and a dielectric layer 24. The gate layer 25 is apart disposed between the anode plate 10 and the cathode plate 20. The anode plate 10 is subjected to a potential difference to drain electron beams emitted from the electron-emission source layer 23. The voltage provided by the gate layer 25 accelerates the electron beams to impinge the phosphor layer 13 of the anode plate 10, so as to generate visible light.
The display includes a plurality of pixels composed of red, blue and green cathode and anode units. One anode unit with one of the three primary colors can be called “sub-pixel”. The different composition of the phosphor layer 13 provides three primary colors; however, the lights with different color emitted by the phosphors have different luminescent efficiencies. As a result, although the electron beams emitted from the electron-emission source layer carry the same kinetic energy, the brightness efficiencies of different colored phosphors are different. Thus, the brightness of the different colored lights emitted from the phosphor layer are substantially different. Typically, the brightness ratio of the red, blue and green colored light is about 2:1:7. Therefore, color or brightness distortion at one pixel or on whole screen always occurs. In order to solve this problem, conventional FEDs use a complex control circuit to compensate the inconsistent luminescent efficiencies. But this solution costs a lot. It is thus very uneconomic.
Another approach to resolve the discrepancies in luminescent efficiencies is to adjust the thickness or area size of the phosphor layer 13. The drawback of such approach is that it is very difficult to make the thickness or area size of the phosphor layer 13 for the same colored sub-pixels maintain the identicality among different pixels because of extremely numerous pixels in a display to be processed.